Van Allen and Mallis's Comprehensive Catalog and Encyclopedia of Morgan & Peace Dollars lists all known varieties for these popular series. But with thousands of varieties identified, only a small number are of widespread interest to the collecting community. In 2002, authors Jeff Oxman and David Close published the Top 50 Peace Dollar Varieties. Like the Top 100 Morgan Dollar Varieties, it has helped focus collector attention on the most important varieties. While there are some scarcer varieties of course, none of them are too difficult and about a dozen dedicated variety collectors have already completed this interesting set.